The Monthly Newsletter of the Bays Mountain Astronomy Club · the December issue of the...

The Monthly Newsletter of the

BaysMountain AstronomyClub

Edited by Adam Thanz M o re o n t h i s i m a g e .

S e e F N 1

January 2020

Chapter 1

Cosmic Reflections

W i l l i a m Tro x e l - B M A C C h a i r

M o re o n t h i s i m a g e .

S e e F N 2

Greetings fellow BMACers!

HAPPY NEW YEAR! Its 2020…

We had a wonderful meeting for December 2019 with our guest speaker from Davis Gentry from PARI. Davis had a wonderful presentation that everyone seemed to enjoy. He focused on the upcoming programs at PARI, some of the changes that the campus has seen as they position themself as part of the planning for the future of space travel and the preparation for that global space race. I have the contact information for Mr. Gentry if you would like to contact him.

I want to thank everyone for coming out and welcoming him to our club meeting. We had a very good turn out for the end of the year meeting.

I want to share with you that the location that Davis talked about in Chile where he applied for a year study program is featured in the December issue of the Astronomical League's Newsletter, The Reflector.

I wanted to talk a little bit about some upcoming things for 2020 for the club. January, of course, is the Annual Club Dinner. We will be going to The Meadows Restaurant aside of the the MeadowView Resort and Conference Center. The primary date will be January 11, 2020.

The event will start at the bar near the hotel lobby at 5 p.m. for drinks. We'll be seated at 6 p.m. for dinner in the Meadows Restaurant. While we wait for our meals, we'll have a fun astronomical activity.

I need to get a rough count of those that hope to attend. Please contact me at [email protected].

I have the march speaker set and the information will be on the web site very soon. I am still working the February program and updates will be coming within the next few weeks. This is the place that I encourage you if you would like to do a presentation at the club meeting. Let me know and I will be happy to get you scheduled. I am very hopeful that we can arrange some off-site club viewing parties in 2020. I know some of you have expressed interest in this.

William Troxel

Cosmic Reflections

Bays Mountain Astronomy Club Newsletter January 2020 3


S e e F N 3

mailto:[email protected]?subject=BMAC%20Dinner%202020

mailto:[email protected]?subject=BMAC%20Dinner%202020

Before I close this month’s article, I wanted to say that 2019 has seen some changes to club meeting programs, some have been wonderful successes and others have not, however I am not giving up. I will be trying new things that I hope will bring interest to the club. Thank you for your continued support in my effort and please remember this is your club as well as mine. I do place value on your opinions.

I hope to see many of you at the dinner. Until next time….

Clear Skies.

4 Bays Mountain Astronomy Club Newsletter January 2020

Chapter 2

BMACNotes


S e e F N 4

2020 Texas Star Party – Sign Up Now!The great tradition of dark sky observing continues with the 42nd Annual TEXAS STAR PARTY, May 17-24, 2020 near Ft Davis, Texas!

Staying on the Ranch in housing, RV, or camping? Staying off-site in other accommodations? Everyone needs to enter the TSP drawing, held in late January.

You should submit a Registration/Reservation Request Form to ENTER THE TSP DRAWING before January 17, 2020. This will provide you the highest possible chance of being selected as one of the 500 people who will be able to attend TSP this year.

Follow this link to get started!https://texasstarparty.org/get-started/

Comparing Mercury’s and Venus’ Apparent SizesJim Williams sent in this note:

I became curious about the differences in apparent size of Mercury and Venus as they transited the Sun, so I placed a photo of Venus in transit (in H-alpha light) I took back on 6/5/12 beside one of Mercury transiting on the 11th. Both about f14. Quite a difference! Mercury is tiny compared to Venus. If you didn't know Mercury was transiting, you might miss it or mistake it for a sunspot!

BMAC News



S e e F N 3

https://texasstarparty.org/get-started/

https://texasstarparty.org/get-started/


Right: Venus transit of June 5, 2012.

Left: Mercury transit of November 11, 2019.

Both images by Jim Williams

Chapter 3

Celestial Happenings

J a s o n D o r f m a n


S e e F N 5

Let me begin by wishing you all a Happy New Year! Over the past ten years, there have been some amazing discoveries and accomplishments within the astronomical field. The New Horizons spacecraft gave us our first glimpse of Pluto and its moons and then flew past the nicknamed distant Kuiper Belt object, Ultima Thule, now known as 486958 Arrokoth, one year ago. The long theorized existence of gravitational waves were finally detected and we got our first image of a supermassive black hole. What does the next decade hold in store? I'm particularly looking forward to seeing the first woman set foot on the Moon. [Ed.: Would that be Alice?] By the end of the year, we should see the first launch of the SLS spacecraft, which is the rocket that will take humans back to the Moon.

For January and February issues, I thought I would focus my topic on something that you could easily observe - Star Clusters. The winter season provides plenty of dark hours and clearer skies for observing. There are two types of star clusters found in our Milky Way galaxy - open clusters and globular clusters. Each one has its own unique features and stellar characteristics. Let's take a look at each type of cluster and where you can observe

some examples of each in the skies this season. We'll start with globular clusters and explore open clusters in next month's newsletter.

Globular Star ClustersGlobular star clusters are some of the oldest star systems in the Milky Way. They are found within the spherical region called the Halo that surrounds the disk of the galaxy and have random orbits about the center of the galaxy as most formed before the disk had taken shape. Globulars contain 10's of thousands of stars up to a million stars and are spherically shaped with stellar density increasing towards the center. There are roughly 157 currently known globular clusters in our galaxy, with perhaps 10-20 more that remain undiscovered due to the gas and dust in the disk of the Milky Way blocking them from view.

The name is derived from the Latin, globulus - a small sphere. The term globular cluster came from William Herschel in his Catalogue of a Second Thousand New Nebulae and Clusters of Stars published in 1789. Herschel was the first to resolve globulars into individual stars. In the early 1900's, Harlow Shapley estimated the distances to the known globulars using

Jason Dorfman

Celestial Happenings



S e e F N 3

what he thought were Cepheid variables. He found that they were concentrated towards the direction of the brighter portion of the Milky Way and not around the Earth. From this he was able to estimate the size of our galaxy and the position of our Sun within it. He found that we were far from the center of the galaxy. It turned out that what Shapley thought were Cepheid variables were actually RR Lyrae variables, which are fainter than Cepheids. This caused Shapley to overestimate the size of the Milky Way and our distance from the center.

There are several globular clusters that are observable during the winter season. In January, turn your attention to the west for M2 and M15. M2 (Image 1) is a large globular with a dense central core located in Aquarius. It lies 5° north of Beta Aquarii at right ascension (R.A.) of 21h 34m 29.8s and declination (DEC) -0° 43' 55". At magnitude +6.5, it is an easy target for binoculars. Visually the cluster extends about 6 to 8 minutes of arc, with a bright, compressed central region of about 5'. Deep photographs have revealed that the cluster's diameter extends out to about 16' and contains roughly 150,000 stars. M2 is located at a distance of about 37,500 light years and is about 175 light years across. In mid-January, the clusters appear about 20° above the west-southwest horizon an hour after sunset.

M15 (the Pegasus Cluster) (Image 2) is located about 13° north of M2 just off the nose of Pegasus. To find it, start at Enif (epsilon Pegasi), the nose star of Pegasus, and then point your scope

about 4° to the northwest. The celestial position of M15 is at R.A. 21h 30m 57.4s and DEC +12° 15' 26.3". It has some similar characteristics to M2. The cluster is a bit closer, 33,600 light years, and a touch brighter at magnitude +6.2. Its full diameter of 18.0' equates to a true diameter of roughly 175 light years. The core region of M15 is perhaps the densest of all the globular star clusters in our Milky Way. Visually, through amateur scopes, the cluster extends to about 7'. The central core, however, is extremely small compared to the cluster, only about 0.14' or 8.4" in angular diameter. The core of M15 has experienced "core collapse," a process of contraction that is common in the dynamical evolution of globulars.

Another globular that can be seen throughout the winter months is M79 (Image 3), located in the southern part of Lepus at R.A. 5h 25m 0.92s and DEC -24° 30' 26.3". Look due south in mid-January and almost 30° above the horizon just after 10 p.m. Using the two brightest stars of Lepus, Arneb (alpha) and Nihal (beta), imagine a straight line along those two stars. M79 is south along that line about the same distance away as the separation between the stars, roughly 3°. Unlike most of the globulars, M79 is seen far from the center of the galaxy. It is a little over 40,000 light years from us, but about 60,000 light years from the galactic center. Its magnitude is +7.7. The core of M79 is rather dense and appears to be another core collapsed globular.

Wishing you all great views of the skies above for 2020!



Image 1 - Globular Cluster M2

Credit: D. Williams, N. A. Sharp, AURA,

NOAO, NSF


Finder chart for M2 & M15. Image

by Stellarium.


Image 2 - Globular Cluster M15, the Pegasus Cluster

Credit: ESA/Hubble & NASA


Image 3 - Color CCD image of

Globular Cluster M79, taken with the

KPNO 0.9-meter telescope.


Finder chart for M79. Image by

Stellarium.

References:https://en.wikipedia.org/wiki/Globular_cluster (December 6, 2019)

http://www.messier.seds.org/m/m002.html (December 10, 2019)

http://www.messier.seds.org/m/m015.html (December 10, 2019)

http://www.messier.seds.org/m/m079.html


https://en.wikipedia.org/wiki/Globular_cluster

https://en.wikipedia.org/wiki/Globular_cluster







Chapter 4

TheQueenSpeaks

R o b i n B y r n e

This month marks the 15th anniversary of the Huygens lander setting down on the surface of Saturn’s moon, Titan. The lander was named for Christiaan Huygens, who, in 1655, discovered Saturn’s moon, Titan. The lander discovered so much more.

Measuring 9 feet wide, and weighing 700 pounds, the Huygens lander was designed to alight on either a solid or liquid surface, since Titan was suspected of having lakes of liquid methane on the surface. Six scientific interments were incorporated into the lander design. The purpose of the Huygens Atmospheric Structure Instrument (HASI) was to measure both the electrical and physical characteristics of Titan’s atmosphere. The Doppler Wind Experiment (DWE) would measure wind speeds as the probe descended through the atmosphere. The Descent Imager/Spectral Radiometer (DISR) was designed to be used during the descent to study how the atmosphere affected light from the Sun, as well as imaging the landing site from above. The Gas Chromatograph Mass Spectrometer (GC/MS) would measure the composition of the atmosphere. The Aerosol Collector and Pyrolyser (ACP) analyzed aerosols in the atmosphere, in particular, looking for complex organic molecules. And the

Surface Science Package (SSP) would study the physical properties of the landing site.

On October 15, 1997, the Cassini-Huygens Spacecraft began its journey to Saturn. Almost seven years later, in July, 2004, they reached Saturn. Five months after that, the Huygens lander went off on its own to complete its mission. On January 14, 2005, after parachuting for 2 hours and 27 minutes through Titan’s atmosphere, Huygens became the first spacecraft to land on an object in the outer Solar System and the first to land on a moon other than Earth’s moon.

During the descent, Huygens was able to measure the temperature, density, and pressure of Titan’s atmosphere for a large range of altitudes. These measurements allowed scientists to determine the characteristics of Titan’s atmospheric layers, showing evidence of having a well-defined thermosphere, stratosphere, and troposphere, but a negligible mesosphere. The highest temperature measured was -87 ˚C (-125 ˚F) at the top of the stratosphere. At the surface, the temperature was -180 ˚C (-292 ˚F) with an atmospheric pressure 1.47 times Earth’s surface pressure.

Robin Byrne

Happy Birthday Huygens Lander on Titan



S e e F N 3


Left: This image was sent January 14, 2005, by the European Space Agency's Huygens probe

during its successful descent to land on Titan. This is the colored view, following processing to add reflection spectra data,

and gives a better indication of the actual color of the surface.

Initially thought to be rocks or ice blocks, they are more pebble-sized. The two rock-like objects just below the middle of the image are about 15

centimeters (about 6 inches) (left) and 4 centimeters (about 1.5 inches) (center)

across respectively, at a distance of about 85 centimeters (about 33

inches) from Huygens. The surface is darker than originally expected,

consisting of a mixture of water and hydrocarbon ice. There is also evidence of erosion at the

base of these objects, indicating possible fluvial activity.

Image: NASA/JPL/ESA/University of Arizona

Titan: This composite image shows an infrared view of Saturn's moon Titan from NASA's Cassini

spacecraft.

Image: NASA

Right: The Huygens Probe

Wind speeds measured during the descent confirmed that Titan has superrotating winds, which means the winds move faster in the direction the moon rotates than the ground below. The fastest speeds were measured at 120 m/s (270 mph) at an altitude of 120 km (75 miles). The speed and direction varied during the descent, buffeting the Huygens probe for much of its journey. But once on the ground, the winds had slowed to a mere 1 m/s (2.2 mph).

The atmospheric composition was confirmed to be a combination of nitrogen and methane. During the descent, the nitrogen component remained fairly constant, but the methane levels increased, implying liquid methane evaporating into the atmosphere. The evaporation may have been caused by heat from the lander. One question about the methane was related to the possibility of it being generated by life. Based on the isotopes present, it is now thought that the methane was present during the moon’s formation and is stored in the moon in the form of ice. Geologic processes cycle it to the surface over time.

Huygens found that the orange, methane haze that shrouds Titan exists throughout the atmosphere, though in differing densities. The haze particles became both larger and brighter as the probe got closer to the surface. The haze coalesced into clouds of methane ice at upper altitudes, and liquid methane-nitrogen at lower altitudes. It was only near ground level that the haze cleared.

The region where Huygens landed is called the Adiri region, which appears to be a shoreline. Equipped with a battery only designed to power the spacecraft for a total of 3 hours, after landing, Huygens continued sending back data for another 72 minutes. The Cassini spacecraft monitored and imaged Huygens as it descended and after landing. Those images showed what looks like ice pebbles on an orange surface, under a haze of methane. Images of the region also show what look like channels leading into a larger body of liquid. Further analysis showed it to be a dry lakebed. However, Cassini did confirm lakes of liquid hydrocarbons in the polar regions of Titan. It is speculated that the landing region may experience periodic floods.

The surface texture of the landing site was found to be a sandy consistency, but made of ice instead of rock, or similar to snow that has frozen on the top layer. The ice pebbles in the region were rounded, similar to what would happen to rocks eroded by liquids. The pebble sizes are distributed in a way implying they were transported by a river, with larger pebbles upstream, and the pebble size getting smaller the farther downstream you go.

While looking to see if Titan had lightning (it doesn’t), the Huygens probe discovered another electrical phenomenon. Called Schumann resonances, these extremely low frequency signals were generated by an interaction between Saturn’s magnetosphere and Titan’s ionosphere. This generates a current that flows between the atmosphere and a subsurface ocean on


Titan. This was the first evidence for Titan having an ocean beneath its crust.

It’s always amazing how much we can learn from missions to other objects in our Solar System. In just the 3 hours that the Huygens probe operated, our knowledge of Titan and its atmosphere grew exponentially. When people question spending money for the space program, results like this provide a strong argument for continuing to fund space exploration of all kinds. Thank you, Huygens!

References:Huygens (Spacecraft) - Wikipedia

https://en.wikipedia.org/wiki/Huygens_%28spacecraft%29

Cassini Spacecraft Huygens Probe

https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/huygens-probe/

Huygens: The Top 10 Discoveries at Titan

https://sci.esa.int/web/cassini-huygens/-/55221-huygens-titan-science-highlights












Chapter 5

Space Place


S e e F N 6

Orion is the last of a trio of striking star patterns to rise during the late fall and early winter months, preceded by the diminutive Pleiades and larger Hyades in Taurus. All three are easily spotted rising in the east in early January evenings, and are textbook examples of stars in different stages of development.

As discussed in last month’s Notes, the famous Orion Nebula (M42), found in Orion’s “Sword,” is a celestial nursery full of newly-born “baby stars” and still-incubating “protostars,” surrounded by the gas from which they were born. Next to Orion we find the Hyades, in Taurus, with their distinctive “V’ shape. The Hyades are young but mature stars, hundreds of millions of years old and widely dispersed. Imagine them as “young adult” stars venturing out from their hometown into their new galactic apartments. Bright orange Aldebaran stands out in this group, but is not actually a member; it just happens to be in between us and the Hyades. [Ed.: Be aware that the Hyades, though young compared to our Sun, is already leaving the Main Sequence. A good percentage of the cluster’s constituents are large stars and are already dying. The remaining stars are smaller and thus still on the Main Sequence. An overall color temperature of the cluster would be in the red part of the spectrum as the larger stars are in the red giant phase.]

Traveling from Orion to the Hyades we then find the small, almost dipper-shaped Pleiades star cluster (M45). These are “teenage stars,” younger than the Hyades, but older than the newborn stars of the Orion Nebula. These bright young stars are still relatively close together, but have dispersed their birth cocoon of stellar gas, like teenagers venturing around the neighborhood with friends and wearing their own clothes, but still remaining close to home - for now. Astronomers have studied this trio in great detail in order to learn more about stellar evolution.

Figuring the exact distance of the Pleiades from Earth is an interesting problem in astrometry. Knowing their exact distance away is a necessary step in determining many other facts about the Pleiades. The European Space Agency’s Hipparcos satellite determined their distance to about 392 light years away, around 43 light years closer than previous estimates. However, subsequent measurements by NASA’s Hubble Space Telescope indicated a distance of 440 light years, much closer to pre-Hipparcos estimates. Then, using a powerful technique called Very Long Baseline Interferometry (VLBI), which combines the power of radio telescopes from around the world, the distance of the Pleiades was calculated to 443 light years. The ESA’s Gaia

David Prosper

Spot the Young Stars of the Hyades and Pleiades



S e e F N 3



S e e F N 8



S e e F N 9

satellite, a successor to Hipparcos, recently released its first two sets of data, which among other findings show the distance close to the values found by Hubble and VLBI, possibly settling the long-running “Pleiades Controversy” and helping firm up the foundation for follow-up studies about the nature of the stars of the Pleiades.

You can learn more about the Pleiades in the Universe Discovery Guide at bit.ly/UDGMarch, and find out about missions helping to measure our Universe at nasa.gov.

This article is distributed by NASA Night Sky Network. The Night Sky Network program supports astronomy clubs across the USA dedicated to astronomy outreach. Visit nightsky.jpl.nasa.org to find local clubs, events, and more!


http://bit.ly/UDGMarch

http://bit.ly/UDGMarch

http://nasa.gov

http://nasa.gov

http://nightsky.jpl.nasa.org

http://nightsky.jpl.nasa.org

Chapter 6

BMAC

Calendar

and more


S e e F N 7

BMAC Calendar and more



S e e F N 3

Date Time Location NotesB M A C M e e t i n g sB M A C M e e t i n g sB M A C M e e t i n g sB M A C M e e t i n g s

Friday, February 7, 2020 7 p.m.Nature Center

Discovery TheaterProgram: TBA; Free.

Friday, March 6, 2020 7 p.m.Nature Center


Friday, April 3, 2020 7 p.m.Nature Center


S u n W a t c hS u n W a t c hS u n W a t c hS u n W a t c h

Every Saturday & SundayMarch - October

3-3:30 p.m. if clear

At the dam View the Sun safely with a white-light view if clear.; Free.

S t a r W a t c hS t a r W a t c hS t a r W a t c hS t a r W a t c h

March 7, 2020 7 p.m.

ObservatoryView the night sky with large telescopes. If poor weather, an alternate live tour of the night sky will be held in the planetarium theater.; Free. If you are a club member and have completed the Park volunteer program, you are

welcome to help out with this public program. Please show up at least 30 minutes prior to the official start time.Mar. 14, 21, 28, 2020 8 p.m. Observatory

View the night sky with large telescopes. If poor weather, an alternate live tour of the night sky will be held in the planetarium theater.; Free. If you are a club member and have completed the Park volunteer program, you are

welcome to help out with this public program. Please show up at least 30 minutes prior to the official start time.Apr. 4, 11, 18, 25, 2020 8:30 p.m.

ObservatoryView the night sky with large telescopes. If poor weather, an alternate live tour of the night sky will be held in the planetarium theater.; Free. If you are a club member and have completed the Park volunteer program, you are

welcome to help out with this public program. Please show up at least 30 minutes prior to the official start time.

S p e c i a l E v e n t sS p e c i a l E v e n t sS p e c i a l E v e n t sS p e c i a l E v e n t s

Saturday, January 11, 20205 p.m. /6 p.m.

Meadows Restaurant at MeadowView

Annual BMAC Dinner for BMAC members and their families. If you like, meet at the bar at 5 p.m. for drinks. Seating for dinner will be at 6 p.m. The Saturday a week later is the snow date.

Friday, March 27, 2020 TBA TBAMessier Marathon. This is a BMAC members only event. Test your skills at finding Messier objects within a single

night! Weather dependent.

Saturday, May 2, 20201-4:30 p.m.8:30-9:30

p.m.

Nature Center& Observatory

Annual Astronomy Day - Displays et al. on the walkway leading to the Nature Center, 1-4:30 p.m.; Solar viewing 3-3:30 p.m. at the dam; Night viewing 8:30-9:30 p.m. at the observatory. All non-planetarium astronomy

activities are free.

Bays Mountain Astronomy Club

853 Bays Mountain Park Road

Kingsport, TN 37650

(423) 229-9447

www.BaysMountain.com

[email protected]

Annual Dues:

Dues are supplemented by the Bays Mountain Park Association and volunteerism by the club. As such, our dues can be kept at a very low cost.

$16 /person/year

$6 /additional family member

Note: if you are a Park Association member (which incurs an additional fee), then a 50% reduction in BMAC dues are applied.

The club’s website can be found here:

https://www.baysmountain.com/astronomy/astronomy-club/#newsletters

Regular Contributors:

William Troxel

William is the current chair of the club. He enjoys everything to do with astronomy,

including sharing this exciting and interesting hobby with anyone that will

listen! He has been a member since 2010.

Robin Byrne

Robin has been writing the science history column since 1992 and was chair in 1997.

She is an Associate Professor of Astronomy & Physics at Northeast State

Community College (NSCC).

Jason Dorfman

Jason works as a planetarium creative and technical genius at Bays Mountain Park.

He has been a member since 2006.

Adam Thanz

Adam has been the Editor for all but a number of months since 1992. He is the

Planetarium Director at Bays Mountain Park as well as an astronomy adjunct for

NSCC.


http://www.BaysMountain.com

http://www.BaysMountain.com

mailto:[email protected]?subject=

mailto:[email protected]?subject=





Footnotes:1. The Rite of SpringOf the countless equinoxes Saturn has seen since the birth of the solar system, this one, captured here in a mosaic of light and dark, is the first witnessed up close by an emissary from Earth … none other than our faithful robotic explorer, Cassini.Seen from our planet, the view of Saturn’s rings during equinox is extremely foreshortened and limited. But in orbit around Saturn, Cassini had no such problems. From 20 degrees above the ring plane, Cassini’s wide angle camera shot 75 exposures in succession for this mosaic showing Saturn, its rings, and a few of its moons a day and a half after exact Saturn equinox, when the sun’s disk was exactly overhead at the planet’s equator.The novel illumination geometry that accompanies equinox lowers the sun’s angle to the ring plane, significantly darkens the rings, and causes out-of-plane structures to look anomalously bright and to cast shadows across the rings. These scenes are possible only during the few months before and after Saturn’s equinox which occurs only once in about 15 Earth years. Before and after equinox, Cassini’s cameras have spotted not only the predictable shadows of some of Saturn’s moons (see PIA11657), but also the shadows of newly revealed vertical structures in the rings themselves (see PIA11665).Also at equinox, the shadows of the planet’s expansive rings are compressed into a single, narrow band cast onto the planet as seen in this mosaic. (For an earlier view of the rings’ wide shadows draped high on the northern hemisphere, see PIA09793.)The images comprising the mosaic, taken over about eight hours, were extensively processed before being joined together. First, each was re-projected into the same viewing geometry and then digitally processed to make the image “joints” seamless and to remove lens flares, radially extended bright artifacts resulting from light being scattered within the camera optics.At this time so close to equinox, illumination of the rings by sunlight reflected off the planet vastly dominates any meager sunlight falling on the rings. Hence, the half of the rings on the left illuminated by planetshine is, before processing, much brighter than the half of the rings on the right. On the right, it is only the vertically extended parts of the rings that catch any substantial sunlight.With no enhancement, the rings would be essentially invisible in this mosaic. To improve their visibility, the dark (right) half of the rings has been brightened relative to the brighter (left) half by a factor of three, and then the whole ring system has been brightened by a factor of 20 relative to the planet. So the dark half of the rings is 60 times brighter, and the bright half 20 times brighter, than they would have appeared if the entire system, planet included, could have been captured in a single image.The moon Janus (179 kilometers, 111 miles across) is on the lower left of this image. Epimetheus (113 kilometers, 70 miles across) appears near the middle bottom. Pandora (81 kilometers, 50

miles across) orbits outside the rings on the right of the image. The small moon Atlas (30 kilometers, 19 miles across) orbits inside the thin F ring on the right of the image. The brightnesses of all the moons, relative to the planet, have been enhanced between 30 and 60 times to make them more easily visible. Other bright specks are background stars. Spokes -- ghostly radial markings on the B ring -- are visible on the right of the image.This view looks toward the northern side of the rings from about 20 degrees above the ring plane.The images were taken on Aug. 12, 2009, beginning about 1.25 days after exact equinox, using the red, green and blue spectral filters of the wide angle camera and were combined to create this natural color view. The images were obtained at a distance of approximately 847,000 kilometers (526,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 74 degrees. Image scale is 50 kilometers (31 miles) per pixel.The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/. The Cassini imaging team homepage is at http://ciclops.org.Image Credit: NASA/JPL/Space Science Institute

2. Leo RisingA sky filled with stars and a thin veil of clouds.Image by Adam Thanz

3. The Cat's Eye Nebula, one of the first planetary nebulae discovered, also has one of the most complex forms known to this kind of nebula. Eleven rings, or shells, of gas make up the Cat's Eye.Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA)Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov (NASA)

4. Jupiter & GanymedeNASA's Hubble Space Telescope has caught Jupiter's moon Ganymede playing a game of "peek-a-boo." In this crisp Hubble image, Ganymede is shown just before it ducks behind the giant planet.

Footnotes



S e e F N 3

http://saturn.jpl.nasa.gov

http://saturn.jpl.nasa.gov

http://ciclops.org

http://ciclops.org

Ganymede completes an orbit around Jupiter every seven days. Because Ganymede's orbit is tilted nearly edge-on to Earth, it routinely can be seen passing in front of and disappearing behind its giant host, only to reemerge later.Composed of rock and ice, Ganymede is the largest moon in our solar system. It is even larger than the planet Mercury. But Ganymede looks like a dirty snowball next to Jupiter, the largest planet in our solar system. Jupiter is so big that only part of its Southern Hemisphere can be seen in this image.Hubble's view is so sharp that astronomers can see features on Ganymede's surface, most notably the white impact crater, Tros, and its system of rays, bright streaks of material blasted from the crater. Tros and its ray system are roughly the width of Arizona.The image also shows Jupiter's Great Red Spot, the large eye-shaped feature at upper left. A storm the size of two Earths, the Great Red Spot has been raging for more than 300 years. Hubble's sharp view of the gas giant planet also reveals the texture of the clouds in the Jovian atmosphere as well as various other storms and vortices.Astronomers use these images to study Jupiter's upper atmosphere. As Ganymede passes behind the giant planet, it reflects sunlight, which then passes through Jupiter's atmosphere. Imprinted on that light is information about the gas giant's atmosphere, which yields clues about the properties of Jupiter's high-altitude haze above the cloud tops.This color image was made from three images taken on April 9, 2007, with the Wide Field Planetary Camera 2 in red, green, and blue filters. The image shows Jupiter and Ganymede in close to natural colors.Credit: NASA, ESA, and E. Karkoschka (University of Arizona)

5. 47 TucanaeIn the first attempt to systematically search for "extrasolar" planets far beyond our local stellar neighborhood, astronomers probed the heart of a distant globular star cluster and were surprised to come up with a score of "zero".To the fascination and puzzlement of planet-searching astronomers, the results offer a sobering counterpoint to the flurry of planet discoveries announced over the previous months."This could be the first tantalizing evidence that conditions for planet formation and evolution may be fundamentally different elsewhere in the galaxy," says Mario Livio of the Space Telescope Science Institute (STScI) in Baltimore, MD.The bold and innovative observation pushed NASA Hubble Space Telescope's capabilities to its limits, simultaneously scanning for small changes in the light from 35,000 stars in the globular star cluster 47 Tucanae, located 15,000 light-years (4 kiloparsecs) away in the southern constellation Tucana.Hubble researchers caution that the finding must be tempered by the fact that some astronomers always considered the ancient globular cluster an unlikely abode for planets for a variety of reasons. Specifically, the cluster has a deficiency of heavier elements that may be needed for building planets. If this is the case, then planets may have formed later in the universe's evolution, when stars were richer in heavier elements. Correspondingly, life as we know it may have appeared later rather than sooner in the universe.Another caveat is that Hubble searched for a specific type of planet called a "hot Jupiter," which is considered an oddball among some planet experts. The results do not rule out the possibility that 47 Tucanae could contain normal solar systems like ours, which Hubble could not have detected. But even if that's the case, the "null" result implies there is still something fundamentally different between the way planets are made in our own neighborhood and how they are made in the cluster.

Hubble couldn't directly view the planets, but instead employed a powerful search technique where the telescope measures the slight dimming of a star due to the passage of a planet in front of it, an event called a transit. The planet would have to be a bit larger than Jupiter to block enough light — about one percent — to be measurable by Hubble; Earth-like planets are too small.However, an outside observer would have to watch our Sun for as long as 12 years before ever having a chance of seeing Jupiter briefly transit the Sun's face. The Hubble observation was capable of only catching those planetary transits that happen every few days. This would happen if the planet were in an orbit less than 1/20 Earth's distance from the Sun, placing it even closer to the star than the scorched planet Mercury — hence the name "hot Jupiter."Why expect to find such a weird planet in the first place?Based on radial-velocity surveys from ground-based telescopes, which measure the slight wobble in a star due to the small tug of an unseen companion, astronomers have found nine hot Jupiters in our local stellar neighborhood. Statistically this means one percent of all stars should have such planets. It's estimated that the orbits of 10 percent of these planets are tilted edge-on to Earth and so transit the face of their star.In 1999, the first observation of a transiting planet was made by ground-based telescopes. The planet, with a 3.5-day period, had previously been detected by radial-velocity surveys, but this was a unique, independent confirmation. In a separate program to study a planet in these revealing circumstances, Ron Gilliland (STScI) and lead investigator Tim Brown (National Center for Atmospheric Research, Boulder, CO) demonstrated Hubble's exquisite ability to do precise photometry — the measurement of brightness and brightness changes in a star's light — by also looking at the planet. The Hubble data were so good they could look for evidence of rings or Earth-sized moons, if they existed.But to discover new planets by transits, Gilliland had to crowd a lot of stars into Hubble's narrow field of view. The ideal target was the magnificent southern globular star cluster 47 Tucanae, one of the closest clusters to Earth. Within a single Hubble picture Gilliland could observe 35,000 stars at once. Like making a time-lapse movie, he had to take sequential snapshots of the cluster, looking for a telltale dimming of a star and recording any light curve that would be the true signature of a planet.Based on statistics from a sampling of planets in our local stellar neighborhood, Gilliland and his co-investigators reasoned that 1 out of 1,000 stars in the globular cluster should have planets that transit once every few days. They predicted that Hubble should discover 17 hot Jupiter-class planets.To catch a planet in a several-day orbit, Gilliland had Hubble's "eagle eye" trained on the cluster for eight consecutive days. The result was the most data-intensive observation ever done by Hubble. STScI archived over 1,300 exposures during the observation. Gilliland and Brown sifted through the results and came up with 100 variable stars, some of them eclipsing binaries where the companion is a star and not a planet. But none of them had the characteristic light curve that would be the signature of an extrasolar planet.There are a variety of reasons the globular cluster environment may inhibit planet formation. 47 Tucanae is old and so is deficient in the heavier elements, which were formed later in the universe through the nucleosynthesis of heavier elements in the cores of first-generation stars. Planet surveys show that within 100 light-years of the Sun, heavy-element-rich stars are far more likely to harbor a hot Jupiter than heavy-element-poor stars. However, this is a chicken and egg puzzle because some theoreticians say that the heavy-element composition of a star may be enhanced after if it makes Jupiter-like planets and then swallows them as the planet orbit spirals into the star.The stars are so tightly compacted in the core of the cluster – being separated by 1/100th the distance between our Sun and the next nearest star — that gravitational tidal effects may strip nascent planets from their parent stars. Also, the high stellar density could disturb the subsequent migration of the planet inward, which parks the hot Jupiters close to the star.


Another possibility is that a torrent of ultraviolet light from the earliest and biggest stars, which formed in the cluster billions of years ago may have boiled away fragile embryonic dust disks out of which planets would have formed.These results will be published in The Astrophysical Journal Letters in December. Follow-up observations are needed to determine whether it is the initial conditions associated with planet birth or subsequent influences on evolution in this heavy-element-poor, crowded environment that led to an absence of planets.Credits for Hubble image: NASA and Ron Gilliland (Space Telescope Science Institute)

6. Space Place is a fantastic source of scientific educational materials for children of all ages. Visit them at:http://spaceplace.nasa.gov

7. NGC 3982Though the universe is chock full of spiral-shaped galaxies, no two look exactly the same. This face-on spiral galaxy, called NGC 3982, is striking for its rich tapestry of star birth, along with its winding arms. The arms are lined with pink star-forming regions of glowing hydrogen, newborn blue star clusters, and obscuring dust lanes that provide the raw material for future generations of stars. The bright nucleus is home to an older population of stars, which grow ever more densely packed toward the center.NGC 3982 is located about 68 million light-years away in the constellation Ursa Major. The galaxy spans about 30,000 light-years, one-third of the size of our Milky Way galaxy. This color image is composed of exposures taken by the Hubble Space Telescope's Wide Field Planetary Camera 2 (WFPC2), the Advanced Camera for Surveys (ACS), and the Wide Field Camera 3 (WFC3). The observations were taken between March 2000 and January 2009. The rich color range comes from the fact that the galaxy was photographed invisible and near-infrared light. Also used was a filter that isolates hydrogen emission that emanates from bright star-forming regions dotting the spiral arms.Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)Acknowledgment: A. Riess (STScI)

8. Locate Orion rising in the east after sunset to find the Orion Nebula in the “Sword,” below the famous “Belt” of three bright stars. Then, look above Orion to find both the Hyades and the Pleiades. Binoculars will bring out lots of extra stars and details in all three objects, but you can even spot them with your unaided eye!

9. Close-up of the Pleiades, with the field of view of Hubble’s Fine Guidance Sensors overlaid in the top left, which helped refine the distance to the cluster. The circumference of the field of view of these sensors is roughly the size of the full Moon. (Credit: NASA, ESA and AURA/Caltech)


http://spaceplace.nasa.gov

http://spaceplace.nasa.gov

The Monthly Newsletter of the Bays Mountain Astronomy Club · the December issue of the...

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Transcript of The Monthly Newsletter of the Bays Mountain Astronomy Club · the December issue of the...